Linear actuators are mechanical devices that transform electrical energy into mechanical energy to perform repetitive actions that require linear motion. For example, linear actuators can be used in an assembly plant to place caps on bottles, automatically stamp or label mail, cut glass, place chips on circuits, test various buttons or touch areas on electronic devices, and perform a wide variety of other tasks known in the art.
Some tasks may require one or more linear actuators as illustrated in patent application Ser. Nos. 12/622,372 and 12/860,809, the entireties of which are incorporated by reference herein. Typically, a low cost linear actuator has a single pole and a single 24 or 48 volt DC coil linear motor. Less movement occurs in typical low cost linear actuator designs because there is typically only one coil. Consequently, these designs typically provide a limited stroke distance or value (e.g., maximum stroke of 150 mm).
Some applications may require a higher stroke value (e.g., more than 150 mm). Actuators that provide a higher stroke value have longer magnetic circuits. Longer magnetic circuits generate less force than smaller magnetic circuits if a single coil is used. Accordingly, if the linear actuator has only one coil, the force that is generated for a given amperage drops as the stroke value is increased.
To generate more force for a longer stroke, more coils are typically added to actuators. More coils result in shorter magnetic circuits which consequently result in higher forces generated per a given generated current. However, actuators with multiple coils have a greater moving mass, a larger coil assembly, multiple expensive coils, and more expensive magnets as their polarities must be reversed periodically. Thus, traditional multiple coil designs are generally more expensive than their single coil counterparts.
Therefore, there is a need to reduce costs associated with linear coil actuators so that multiple coil linear coil actuators may be manufactured in a less expensive manner.